an introduction to the flood estimation handbook · 2 school of civil engineering and geosciences...

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School of School of Civil Engineering and Geosciences Civil Engineering and Geosciences Chris Kilsby Chris Kilsby University of Newcastle University of Newcastle Building Knowledge for a Changing Climate Building Knowledge for a Changing Climate Precipitation Scenarios

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Page 1: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

School ofSchool ofCivil Engineering and GeosciencesCivil Engineering and Geosciences

Chris KilsbyChris KilsbyUniversity of NewcastleUniversity of Newcastle

Building Knowledge for a Changing ClimateBuilding Knowledge for a Changing Climate

Precipitation Scenarios

Page 2: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

2

School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

RequirementsRequirements

Time resolution� hours and minutes, not days

Space resolution� Specific to sites, not grid boxes

Properties� realistic amounts, intensities, extremes� seasonality� long time series � multiple events

Page 3: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

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School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

ApproachApproach

Stochastic rainfall modelling� To achieve downscaling in time and space� To generate long series� To interface with CRU weather generator

Building on:� UKCIP02 scenarios and UKMO climatology� Consistency with the FEH extremes� 15 years development at Newcastle� The StormPac approach

Page 4: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

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School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

Rainfall modellingRainfall modelling

The GNSRP model� A stochastic rainfall modelling system� Generalised Neyman-Scott Rectangular Pulses� Can generate arbitrarily long series (e.g. 1000

years) of rainfall� Applied to historic, control and future climates� Reproduces key statistical properties of rainfall

series, e.g. mean, variance, dry hours, 2, 5, 10, 25year annual maxima);

� Time resolution of 1-hour or 1-day

Page 5: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

5

School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

Rainfall modellingRainfall modelling

� Storm origins arrive in aPoisson process

� Each origin generates arandom number of rain cells

� A rectangular pulse isassociated with each rain cell

� The total rainfall at any timeis the sum of all active raincells

time

time

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inte

nsity

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tota

l int

ensi

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Page 6: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

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School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

Work Plan - 1Work Plan - 1

Historic case� Set up the GNSRP model for the whole UK

using the MetOffice/UKCIP 5-kmclimatology.

� Parameterise to match observed 1961-1990 rainfall:

� means, variance, proportion dry hours etc� return period rainfalls - 2,5,10 or 25 year events

using observed data and FEH DDF model

Page 7: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

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School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

Work Plan - 1Work Plan - 1

18 sitesin 9 regions> 10 years

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Dyce

Hemsby

Warcop

Leeming

Tulloch

Ringway

Manston

Cranwell

Leuchars

Heathrow

Turnhouse

Stornoway

Yeovilton

St Mawgan

Aldergrove

AbbotsinchEskdalemuir

Hillsborough

ourly rainfall recordsRegions

CEEESNEENINSNWESEESSSWE

$ Hourly gaug

Page 8: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

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School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

Work Plan - 1Work Plan - 1

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RegionsCEEESNEENINSNWESEESSSWE

# Daily gaug

Daily rainfall records204 sitesin 9 regions40 years

Page 9: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

9

School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

Work Plan - 2Work Plan - 2

Future climate� Parameterise for the whole UK for future

climates by using control and future outputfrom HAdRM3

Sub-hourly resolution� Use cascade model to disaggregate data

from 60 � 30 � 15 minute level� Reliability to be established below 15 minute

� depends on validation data

Page 10: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

10

School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

Work Plan - 3Work Plan - 3

� Interface from GNSRP model to CRU dailyWG.

� Extend model to allow for changingproportion of convective/frontal rainfall infuture climate

Page 11: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

11

School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

Summary - DeliverablesSummary - Deliverables

Rainfall model� for use by partners;� within the project;� to generate rainfall series;� at any site in UK� arbitrary length� time resolution of 1-day, 1-hour and below� control and future climates� reproduces observed extreme rainfall (up to

at least 25 year return period)

Page 12: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

12

School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

DataData

Observed daily rainfalldata 1961-2000

Daily rainfall data fromRCMs 1961-1990 and2070-2100

Page 13: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

13

School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

ChangesChanges

East Scotland 10-day

22 5 10 25 50 100 200 500

0

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-2 -1 0 1 2 3 4 5 6 7

Reduced Variate

Rain

fall

(mm

)

61-7071-8081-9091-00

50-yr event

Page 14: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

14

School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

What does this mean for the UK?What does this mean for the UK?

Change in recurrence interval for a 50-year event in 1961-1990 during 1991-2000

ES 1 in 8 yearSS 1 in 11 yearNS 1 in 25 yearNWE 1 in 25 yearNEE 1 in 25 year

Page 15: An Introduction to the Flood Estimation Handbook · 2 School of Civil Engineering and Geosciences Requirements Time resolution Ł hours and minutes, not days Space resolution Ł Specific

15

School of Civil Engineering and GeosciencesSchool of Civil Engineering and Geosciences

Future projectionsFuture projections

� (a) and (b) showHadRM2 projected %change in magnitude of10-yr and 50-yr 1 dayevent during 2080-2100

� (c) and (d) show samefor HadRM3 (UKCIP02)scenarios

(d)(c)

(b)(a)

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